1 /* 2 * Copyright (C) 2001-2002 Sistina Software (UK) Limited. 3 * Copyright (C) 2008 Red Hat, Inc. All rights reserved. 4 * 5 * Device-mapper snapshot exception store. 6 * 7 * This file is released under the GPL. 8 */ 9 10 #ifndef _LINUX_DM_EXCEPTION_STORE 11 #define _LINUX_DM_EXCEPTION_STORE 12 13 #include <linux/blkdev.h> 14 #include <linux/device-mapper.h> 15 16 /* 17 * The snapshot code deals with largish chunks of the disk at a 18 * time. Typically 32k - 512k. 19 */ 20 typedef sector_t chunk_t; 21 22 /* 23 * An exception is used where an old chunk of data has been 24 * replaced by a new one. 25 * If chunk_t is 64 bits in size, the top 8 bits of new_chunk hold the number 26 * of chunks that follow contiguously. Remaining bits hold the number of the 27 * chunk within the device. 28 */ 29 struct dm_exception { 30 struct list_head hash_list; 31 32 chunk_t old_chunk; 33 chunk_t new_chunk; 34 }; 35 36 /* 37 * Abstraction to handle the meta/layout of exception stores (the 38 * COW device). 39 */ 40 struct dm_exception_store; 41 struct dm_exception_store_type { 42 const char *name; 43 struct module *module; 44 45 int (*ctr) (struct dm_exception_store *store, char *options); 46 47 /* 48 * Destroys this object when you've finished with it. 49 */ 50 void (*dtr) (struct dm_exception_store *store); 51 52 /* 53 * The target shouldn't read the COW device until this is 54 * called. As exceptions are read from the COW, they are 55 * reported back via the callback. 56 */ 57 int (*read_metadata) (struct dm_exception_store *store, 58 int (*callback)(void *callback_context, 59 chunk_t old, chunk_t new), 60 void *callback_context); 61 62 /* 63 * Find somewhere to store the next exception. 64 */ 65 int (*prepare_exception) (struct dm_exception_store *store, 66 struct dm_exception *e); 67 68 /* 69 * Update the metadata with this exception. 70 */ 71 void (*commit_exception) (struct dm_exception_store *store, 72 struct dm_exception *e, int valid, 73 void (*callback) (void *, int success), 74 void *callback_context); 75 76 /* 77 * Returns 0 if the exception store is empty. 78 * 79 * If there are exceptions still to be merged, sets 80 * *last_old_chunk and *last_new_chunk to the most recent 81 * still-to-be-merged chunk and returns the number of 82 * consecutive previous ones. 83 */ 84 int (*prepare_merge) (struct dm_exception_store *store, 85 chunk_t *last_old_chunk, chunk_t *last_new_chunk); 86 87 /* 88 * Clear the last n exceptions. 89 * nr_merged must be <= the value returned by prepare_merge. 90 */ 91 int (*commit_merge) (struct dm_exception_store *store, int nr_merged); 92 93 /* 94 * The snapshot is invalid, note this in the metadata. 95 */ 96 void (*drop_snapshot) (struct dm_exception_store *store); 97 98 unsigned (*status) (struct dm_exception_store *store, 99 status_type_t status, char *result, 100 unsigned maxlen); 101 102 /* 103 * Return how full the snapshot is. 104 */ 105 void (*usage) (struct dm_exception_store *store, 106 sector_t *total_sectors, sector_t *sectors_allocated, 107 sector_t *metadata_sectors); 108 109 /* For internal device-mapper use only. */ 110 struct list_head list; 111 }; 112 113 struct dm_snapshot; 114 115 struct dm_exception_store { 116 struct dm_exception_store_type *type; 117 struct dm_snapshot *snap; 118 119 /* Size of data blocks saved - must be a power of 2 */ 120 unsigned chunk_size; 121 unsigned chunk_mask; 122 unsigned chunk_shift; 123 124 void *context; 125 126 bool userspace_supports_overflow; 127 }; 128 129 /* 130 * Obtain the origin or cow device used by a given snapshot. 131 */ 132 struct dm_dev *dm_snap_origin(struct dm_snapshot *snap); 133 struct dm_dev *dm_snap_cow(struct dm_snapshot *snap); 134 135 /* 136 * Funtions to manipulate consecutive chunks 137 */ 138 # if defined(CONFIG_LBDAF) || (BITS_PER_LONG == 64) 139 # define DM_CHUNK_CONSECUTIVE_BITS 8 140 # define DM_CHUNK_NUMBER_BITS 56 141 142 static inline chunk_t dm_chunk_number(chunk_t chunk) 143 { 144 return chunk & (chunk_t)((1ULL << DM_CHUNK_NUMBER_BITS) - 1ULL); 145 } 146 147 static inline unsigned dm_consecutive_chunk_count(struct dm_exception *e) 148 { 149 return e->new_chunk >> DM_CHUNK_NUMBER_BITS; 150 } 151 152 static inline void dm_consecutive_chunk_count_inc(struct dm_exception *e) 153 { 154 e->new_chunk += (1ULL << DM_CHUNK_NUMBER_BITS); 155 156 BUG_ON(!dm_consecutive_chunk_count(e)); 157 } 158 159 static inline void dm_consecutive_chunk_count_dec(struct dm_exception *e) 160 { 161 BUG_ON(!dm_consecutive_chunk_count(e)); 162 163 e->new_chunk -= (1ULL << DM_CHUNK_NUMBER_BITS); 164 } 165 166 # else 167 # define DM_CHUNK_CONSECUTIVE_BITS 0 168 169 static inline chunk_t dm_chunk_number(chunk_t chunk) 170 { 171 return chunk; 172 } 173 174 static inline unsigned dm_consecutive_chunk_count(struct dm_exception *e) 175 { 176 return 0; 177 } 178 179 static inline void dm_consecutive_chunk_count_inc(struct dm_exception *e) 180 { 181 } 182 183 static inline void dm_consecutive_chunk_count_dec(struct dm_exception *e) 184 { 185 } 186 187 # endif 188 189 /* 190 * Return the number of sectors in the device. 191 */ 192 static inline sector_t get_dev_size(struct block_device *bdev) 193 { 194 return i_size_read(bdev->bd_inode) >> SECTOR_SHIFT; 195 } 196 197 static inline chunk_t sector_to_chunk(struct dm_exception_store *store, 198 sector_t sector) 199 { 200 return sector >> store->chunk_shift; 201 } 202 203 int dm_exception_store_type_register(struct dm_exception_store_type *type); 204 int dm_exception_store_type_unregister(struct dm_exception_store_type *type); 205 206 int dm_exception_store_set_chunk_size(struct dm_exception_store *store, 207 unsigned chunk_size, 208 char **error); 209 210 int dm_exception_store_create(struct dm_target *ti, int argc, char **argv, 211 struct dm_snapshot *snap, 212 unsigned *args_used, 213 struct dm_exception_store **store); 214 void dm_exception_store_destroy(struct dm_exception_store *store); 215 216 int dm_exception_store_init(void); 217 void dm_exception_store_exit(void); 218 219 /* 220 * Two exception store implementations. 221 */ 222 int dm_persistent_snapshot_init(void); 223 void dm_persistent_snapshot_exit(void); 224 225 int dm_transient_snapshot_init(void); 226 void dm_transient_snapshot_exit(void); 227 228 #endif /* _LINUX_DM_EXCEPTION_STORE */ 229